Protective effect of metallothionein on cadmium toxicity in isolated rat hepatocytes.

An isolated rat hepatocyte preparation was used to study the cellular toxicity of cadmium and the protective effects of metallothionein on cadmium-induced toxicity. Exposure of primary suspension cultures of isolated rat hepatocytes to Cd2+ (0-35.7 microM) for 15 min resulted in a dose-dependent reduction in the synthesis of cellular proteins during a subsequent 6 h incubation. Such inhibition could not be correlated with cellular lethality or gross membrane damage. Pre-induction of metallothionein in hepatocytes by zinc treatment in vivo of donor rats protected hepatocytes in vitro from cadmium-induced inhibition of protein synthesis. The protective effects in zinc-pre-induced hepatocytes are not due to alterations in the level of total cellular cadmium, but could be accounted for by the redistribution of intracellular cadmium in the presence of high levels of zinc-metallothionein. The data suggest that metallothionein exerts its protective effect by a kinetic detoxification mechanism, i.e. a decrease in reactive intracellular cadmium.     

Effects of cadmium toxicity upon the in vivo and in vitro activity of proteins and five enzymes in blood serum and tissue homogenates of Mugil cephalus

This study reports changes in total protein and certain liver, heart, gill and serum enzymes after exposing fish or tissue homogenates and serum to Cd, i.e. in vivo and in vitro effects. Five enzymes were selected for assay; aspartate amino transferase (AAT), alanine amino transferase (A1AT), alkaline phosphatase (A1P), acid phosphatase (ACP) and lactic dehydrogenase (LDH). Total protein content in the exposed fish showed an increase in the liver, gill and serum while there was no change in heart protein. The sensitivity of the five assayed enzymes to Cd varied in different tissues. Gill AAT, A1AT were the most sensitive. Liver A1P and heart LDH showed the maximum inhibition at higher Cd concentrations.     

The isolation,characterization and sequence of two divergent β-tubulin genes from soybean (Glycine max L.)

Two divergent -tubulin genes (designated S-1 and S-2) were isolated by screening a soybean genomic library with a Chlamydomonas reinhardtii -tubulin cDNA probe. Restriction fragment analysis of the clones recovered, and of soybean genomic DNA, indicated that these represent two unique classes of structurally different -tubulin genes in the soybean genome. However, it is possible that unidentified members of these classes or additional highly divergent classes of -tubulin genes (thus far undetected) exist in the soybean genome. The S-1 and S-2 genomic clones were sequenced, revealing that both are potentially functional genes which would encode -tubulins of 445 and 449 amino acids, respectively. A comparison of their derived amino acid sequences with -tubulins from several organisms showed that they are most homologous to Chlamydomonas -tubulin (85–87%), with lesser degrees of homology to -tubulins of vertebrate species (79–83%), Trypanosoma brucei (80–81%) and Saccharomyces cerevisiae (66–68%). The amino acid sequences of S-1 and S-2 are as divergent from each other as they are from the Chlamydomonas -tubulin. The amino acids at the diverged positions in S-2 are nearly all conservative substitutions while in S-1, 18 of the 69 substitutions were non-conservative. Both soybean -tubulin genes contain two introns in exactly the same positions. The first soybean intron is located in the same position as the third intron of the Chlamydomonas -tubulin genes. Codon usage in the two soybean -tubulins is remarkably similar (D ²=0.87), but differs from codon usage in other soybean genes.     

Regulation of the formation of protease inBacillus megaterium

During the growth of the asporogenous variant ofBacillus megaterium KM in medium containing NO₃ ⁻ as nitrogen source, the relative rate of extracellular protease synthesis is higher than in the presence of NH₄ ⁺. It approaches the relative rate of enzyme synthesis at the incubation of cells in nitrogen-free medium with glucose. This supports the suggestion that even amino acids which are synthesized endogenously slow down the protease production. In the postlogarithmic or stationary phase the protease production stops. The interruption of enzyme production does not appear as a result of insufficient aeration in a dense suspension, or of accumulation of amino acids or their metabolites in cells. The non-growing cells retain their ability to renew the enzyme synthesis when transferred into a fresh medium, even into a medium without nitrogen source. In the same way it is possible to “induce” the protease production, if Ca²⁺ is added to cells in the stationary phase when the population was grown in the Ca²⁺ free medium. The amount of enzyme produced at the expense of protein turnover by the non-growing populations is sufficient for the fast hydrolysis of exogenous protein in the medium and for assuring the influx of a sufficient amount of peptides into the cells. In such a case the growth of the culture is therefore very quickly renewed.     

Assessment of faba bean (Vicia faba) response to inoculation with Rhizobium leguminosarum in clay loam Nile Delta soil

A field experiment was conducted to assess the response to inoculation with rhizobia in a clay loam soil of the Nile Delta using faba bean (Vicia faba) for two successive winter seasons (1985/6 and 1986/7). Three selected strains of Rhizobium leguminosarum, TAL 634, NRC 65 and TAL 1400, were used singly or in combination as peat-based inocula in 1985/6 winter season. Strain TAL 1400 was replaced by strain F9 in the 1986/7 winter season. A significant seed yield response was obtained only with strain TAL 1400, in the 1985/6 season. In the 1986/7 season, no significant yield response was observed with any of the strains. The serotyping of nodules collected in the 1985/6 season showed that strain TAL 1400 was more competitive than either the indigenous rhizobia or the two inoculant strains. However, the majority of nodules formed in the 1986/7 season were formed from strains other than the inoculant ones.     

Cytokeratin expression in human tongue epithelium.

The epithelium of the human tongue shows diverse morphological variations from one site to another and even within the epithelium of the same papilla. This complexity has led to confusion regarding tongue epithelium as being orthokeratinized, parakeratinized, or nonkeratinized. Cytokeratins have been shown to characterize different epithelia. The present paper describes cytokeratin expression by adult tongue epithelia and relates their distribution to morphology. Six healthy human tongue specimens were obtained after plastic surgery and cytokeratin expression was investigated immunohistochemically, using a panel of 15 antibodies for cytoskeletal proteins, and biochemically using two-dimensional gel electrophoresis. The results showed that the ventral and lateral surfaces of the tongue are related to the nonkeratinizing stratified squamous epithelia, esophageal type, whereas the dorsal surface showed mixed expression of cytokeratins. In the tip of filiform and on the surface of fungiform papillae, cytokeratins of terminal differentiation are expressed as skin type; and in the rest of the papillae as well as in interpapillary areas, the epithelium expresses esophageal type cytokeratins. Certain simple epithelial cytokeratins were found in taste buds. Cytokeratin 19 was also detected in the basal cell layer of all esophageal type epithelia in the tongue. The present results provide basis for studies on the biological events in epithelial differentiation during development and in pathology.     

Tissue-specific expression in the salivary glands of transgenic mice.

Using a DNA construct, named Lama, derived from the murine parotid secretory protein (PSP) gene, we have obtained salivary gland specific gene expression in transgenic mice. Lama is a PSP minigene and allows analysis of the PSP gene 5' regulatory region by transgenesis. We show here that the regulatory region included in Lama with 4.6 kb of 5' flanking sequence is sufficient to direct expression specifically to the salivary glands. The expression level in the parotid gland is only about one percent of the PSP mRNA level, while that of the sublingual gland is near the PSP mRNA level. This suggests significant differences in the PSP gene regulation in the two glands. In addition, Lama is a secretory expression vector in which cDNAs or genomic fragments can be inserted. We demonstrate that the Lama construct can direct the expression of a heterologous cDNA encoding the C-terminal peptide of human factor VIII to salivary glands and that the corresponding peptide is secreted into saliva.     

Maternal hair zinc concentration in neural tube defects in Turkey

Hair zinc concentration was measured in samples taken from 57 mothers who delivered infants with neural tube defects (NTD) (mainly anencephaly). Control groups consisted of 30 healthy mothers with normal offspring and 37 nonpregnant women from middle-income backgrounds. Zinc concentration was also measured in the hair of eight infants with NTD (four being anencephalic). The mean maternal hair zinc concentration in the NTD group (128.2 +/- 38.9 micrograms/g) was lower than that of the control women (p less than 0.001), whereas the mean hair zinc level of malformed babies (250.4 +/- 85.2 micrograms/g) was significantly higher than that of normal infants (193.4 +/- 39.2 micrograms/g) (p less than 0.05). Maternal nutritional zinc deficiency was thought to be one of the factors responsible for NTD in Turkey.     

Coumarin sulphates of Seseli libanotis

Three new sulphate ester salts derived from known coumarin alcohols–one of them tertiary–have been obtained from roots of Seseli libanotis subsp. eu-libanotis. Their structures were established as (2′S)-rutaretin-1″-sulphate, (3′R)-lomatin-3′-sulphate and (3′R,4′R)-khellactone-3′-sulphate. They were together with their parent alcohols characterized by ¹³C NMR spectroscopy. It is the first report on coumarin sulphates in plants.